The characters that have been so far used in the delimitation of the
fossil species (Tab. 3) were compared to those adopted for the Recent species both by
Wilks & Woelkerling (1995) from the southern Australia and by Basso (1995) from the
Tyrrhenian Sea (Mediterranean). This comparison has provided the following results. At
least seven characters relating to vegetative features and one relating to reproductive
ones have been used by previous authors to delimit fossil species of Lithothamnion
(Tab. 3). Only one of these (plant habit, character 1) has been found useful in delimiting
the Recent species as an ancillary character (Wilks & Woelkerling, 1995). The
remaining characters are considered too variable (characters 2-8). Except for a few
species, the numerical characters are thus not sufficiently reliable to discriminate the
species, as already demonstrated for Neogene Lithophyllum (Braga & Aguirre,
1995). In the present-day species both from the Tyrrhenian Sea (Basso, 1995) and southern
Australia (Wilks & Woelkerling, 1995), it seems that the diagnostic characters at
species level are the shape and structure of the conceptacles (in particular those
associated with tetra/bisporangial conceptacle roof anatomy).

Remarks. L. sp. 1 shows analogies with Lithothamnium
aesitante described by Francavilla et al. (1970) from the Priabonian of the Colli
Berici, however, the authors did not illustrated the species except for a photos of the
multiporate conceptacles, which are smaller than those of L. sp. 1. Bassi (1995a)
sampled the same locality of Francavilla et al. (1970) and described L. sp. 1 which
may be compared to L. sp. 1 herein described.

Mesophyllum is seems to be the only genus of the subfamily
Melobesioideae with a "crustose to fruticose but not taeniform" growth-forms
(pag. 390) and with "a predominantly coaxial core" (pag. 392, Woelkerling &
Irvine, 1986; Woelkerling, 1988). Woelkerling & Harvey (1993) delimited Mesophyllum
from other melobesioid genera on the basis of the anatomy of spermatangial conceptacles.
However, all melobesioid species which have had a predominance of coaxial core, have been
ascribed to Mesophyllum. This suggests that, while M. may not be designed
only on the basis of a coaxial core, this character is strongly associated with the genus,
and may be useful for identification when sexual material is not available, as is often
the case with populations of M. species (Keats & Chamberlain, 1994; Keats &
Maneveldt, 1997).

The coaxial core arrangement has thus been one of the most important
features used in the fossil material to ascribe several specimens to the genus Lithophyllum.
The lack of tetra/bisporangial conceptacles, and thus the impossibility to recognize the
conceptacle roof characters (uniporate or multiporate) did not preclude the establishment
of new species (Lemoine, 1928; Conti, 1950; Mastrorilli, 1968). The main difference in the
vegetative anatomy between Lithophyllum and Mesophyllum is that the latter
is characterized by cell fusions. According to the recognition of this cell characters,
several fossil species previously identified as Lithophyllum, should be revised.

Vegetative anatomy. Thallus monomerous; internal longitudinal
organisation radial, composed by a single system of cell filaments that form a central
coaxial core with arching tiers of cells when viewed in radial section; cells 27-32

mm (M= 29, s.d. 3) long and 10-16 mm (M= 13, s.d. 3) in diameter in core region;
main dimensions found in the axial part of the thallus. Distal portions of the filaments
arch upwards towards the dorsal thallus surface or slant downwards towards the ventral
thalus surface in varying degree; the cells of this portions are shorter (about 12 mm in diameter) than those in the coaxial core and
usually micritized. No epithallial cells were recognized. Cells of adjacent filaments
connected laterally by cell fusions. Conceptacles not found.

Remarks. The thallus monomerous with a central coaxial core
together with cell fusions enable the specimens to be ascribed to Mesophyllum (see
Woelkerling & Irvine, 1986; Keats & Chamberlain, 1994).

Among the Palaeogene species identified in the Piedmont Basin
(Mastrorilli, 1968) and in Veneto (Mastrorilli, 1973; Francavilla et al., 1970; Vannucci,
1970), Lithophyllum simplex Lemoine 1927 and Lithophyllum symetricum Lemoine
1927 show analogies as far as the thallus organisation of M. sp. 1 is concerned.
The descriptions of these species made by Mastrorilli (1968), Francavilla et al. (1970),
and Vannucci (1970) report the dominant coaxial core filament arrangement of the thallus
and the absence of conceptacles. Moreover, the illustration of the species show
predominant cell fusions which thus enable the specimens to be identified as Mesophyllum
and not as Lithophyllum.

In considering the relationships of Spongites with other
Corallinaceae, Hydrolithon "presumably" differs from Spongites in
possessing a unistratose rather than a multistratose core ("medullar
hypothallium", Woelkerling, 1985a), and Neogoniolithon in having coaxial core
filamments (Braga et al., 1993). Further discussions about the relationships between Spongites
and H. have been provided by Penrose & Woelkerling (1992). At present, S.
is delineated from Neogoniolithon by the absence of coaxial core filaments
(Woelkerling, 1985a, 1988). It seems that reproductive, rather than vegetative, characters
provide a basis for generic differentiation in the Mastophoroideae; vegetative characters
may, however, often be of diagnostic value at species level (Chamberlain, 1993). The
generic diagnosis proposed by Penrose (1992) and Penrose & Woelkerling (1992) are,
therefore, accepted.

In most identification keys of fossil corallines the recognition of
uniporate conceptacles and non-coaxial core filament ("plumose" arrangement)
defined Leptolithophyllum and Tenarea (pag. 95-96, Conti, 1950) and sometime
Lithophyllum (pag. 37-39, Lemoine, 1939). According to Woelkerling (1988), Leptolithophyllum
is not recognized as a valid taxon (p. 103-104); Tenarea and Lithophyllum,
both lacking cell fusions, belong to the subfamily Lithophylloideae.

Mastrorilli (1958) defined L. malarodai, the type locality is
Fontanafredda, Monti Lessini, Lutetian). Afterwards the same author recognized two new
species in the Oligocene-Miocene deposits near Schio-Vicenza: L. lateporatum and L.
vicetinum (1973). Their peculiar characters are represented by the conceptacle shapes:
the arcuate conceptacle walls, the flat floors, and the long pore canal make analogies
between these species. The schematic drawings and the photos of these species reported by
Mastrorilli (1958, 1973) show uniporate conceptacles which are comparable to those of S.
sp. 1. In the photos 2 and 3 of pl. 6 (Mastrorilli, 1973) showing L. lateporatum
and L. vicetinum respectively, it is possible to recognize the growth rhythms of
the thallus and the absence of a well defined separation of the cells; this latter is
usually due to the fusions between them. The non-coaxial cell filaments, the cell fusions,
and the uniporate conceptacles allow L. malarodai, L. lateporatum, and L.
vicetinum to Spongites to be recognized. Nevertheless, no revision of the
holotypes and the original collections was made thus far.

mm (M= 160, s.d. 10) high and 270-300 mm (M= 285, s.d. 15) in diameter. Pore canal
conical in shape 200 mm high and
about 50 mm in diameter; depth of
tetra/bisporangial conceptacle chamber floor of 10 cells; central columella about 40-50 mm high. Only one uniporate conceptacle differs in
shape and size from the others (Fig. 9); it is flask in shape with chamber 80 mm high and 540 mm in diameter; flat floor with marginal depressions about 30 mm depth. Pore canal about 240 mm high, 30 mm and 50 mm in diameter
at the base and top respectively; cell filaments protruding into the canal.

Remarks. Spongites sp. 2 differs from Spongites sp. 1
in having larger conceptacle chambers and larger pore canals which are conical in shape.

mm (M= 200, s.d. 6) high and 463-477 mm (M= 470, s.d. 7) in diameter; depth of tetra/bisporangial conceptacle
chamber floor of about 10 cells. Pore canal about 150 mm long and 80 mm in
diameter, lined by numerous small cells arranged in 10-11 filaments subparallel to the
roof surface.

Remarks. Spongites sp. 3 differs from S. sp. 1 in
having larger conceptacle chambers and conical pore canals; S. sp. 3 difffers from S.
sp. 2 in having larger conceptacles and shorter pore canals. S. sp. 3 show
similarities with S. sp. described by Bassi (1995a) in the Priabonian of the Colli
Berici, however, this latter has a larger conceptacle diameter than the S. sp. 3.

Tetra/bisporangial conceptacles uniporate; only two tangential section
of conceptacles were found; they show typical uniporate chambers which are respectively
230-250

mm high and 460-480 mm in diameter. The random sections do not show
the pore canal.

Remarks. N. sp. 2 differs from N. sp. 1 in having a
thicker peripheral region, higher and with different shape conceptacles.

The thick coaxial core reminds those of Lithophylum contii
Mastrorilli s.a. (pls. 25-26; Fravega & Vannucci, 1987) and of Lithophyllum
giammarini described by Vannucci (1970) (Lithophyllum giammarinoi is considered
a junior synonym of Lp. contii; Fravega & Vannucci, 1987). No recent revision
of the type collections of these species has been made so far.

L. contii Mastrorilli is characterized by a thick core in which
cell fusions connecting the contiguous filaments are present. They have never been
described by the several authors who studied this species (Mastrorilli, 1967, 1968;
Vannucci, 1970; Francavilla et al., 1970; Fravega & Vannucci, 1987), however, it is
possible to recognize them in the photos 2 and 4 of pl. 25 representing the original types
(in Fravega & Vannucci, 1987). The conceptacles of N. sp. 2 were always
recorded in tangential sections which do not show the pore canals. The shape and the size
of these conceptacles are, however, comparable to those reported by Fravega & Vannucci
(1987), who affirm that "i concettacoli in sezione tangenziale appaiono come
cavit ovoidali di dimensioni minori (rispetto alla sezione assiale; n.d.r.) (35-90

mm x 160-200 mm)". The occurrence of cell fusions characterize the members of the
subfamilies Melobesioideae and Mastophoroideae; moreover, the presence of uniporate
conceptacles is typical of the mastophoroid genera (Braga et al., 1993). The types of Lithophyllum
contii need thus to be revised and eventually reassigned to a different genus (Neogoniolithon?).

Remarks. According to Braga et al. (1993) and Woelkerling (1988),
diagnostic features of Lithoporella are: thin dimerous thallus with large cells,
presence of cell fusions, and uniporate tetra/bisporangial conceptacles. The dimerous
thallus consists of multiple overgrowths of large cells.

mm high and 352-400 mm in diameter, with pore canal about 100 mm high and 70 mm in
diameter.

Remarks. most species of Lithoporella recorded from the
Eocene to the Recent were assigned to melobesioides (which is also the type species
of the genus). This species is well known both in the fossil (Cretaceous) and Recent
material.

mm high and 200 mm in diameter in tangential sections; no measures of the pore canal were
taken.

Remarks. L. cf. minus differs from L.
melobesioides only in having smaller cells. Although there is high intraspecific
variability, the thallus characters described above allow the comparison of our specimens
to L. minus which has been always recorded in Eocene deposits to be made. The
separation between these two species, however, is based only on the cell sizes (Johnson,
1964b), which does not seem a valid character at species level. A revision of L. minus
together with the other species described in fossil material, and an account of L.
melobesioides are needed.

Remarks. According to Braga et al. (1993), the occurrence of cell
fusions characterizes the members of the subfamilies Mastophoroideae and Melobesioideae.
As no conceptacles were found in the specimens above described, it is impossible to infer
them to any genus. Large poligonal cells, as described for our specimens, were considered
to belong to Hydrolithon by Martn et al. (1993). According to Penrose &
Woelkerling (1992), the diagnostic features which distinguish Hydrolithon and Spongites
are restricted to the pore canals of tetrasporangial conceptacles. Hydrolithon is
characterized by conceptacles lined by a ring of elongate cells that arise from filaments
interspersed amongst sporangial initials; they do not protrude into the canal, and are
oriented more or less perpendicularly to the roof surface. For the relationships to Spongites,
see the above mentioned remarks.

The absence of the tetra/bisporangial conceptacles in our specimens,
however, does not allow a certain taxonomic determination at genus level to be made.
Further studies concerning the conceptacle characters are thus needed.

According to ICBN rules, Woelkerling (1988) and Moussavian & Kuss
(1990) have definitively demonstrated and accepted the priority of Sporolithon
Heydrich 1897 over Archaeolithothamnium Rothpletz 1891/Archaeolithothamnion
Rothpletz 1891 ex Foslie 1898. This priority is justified by article 34.1 of ICBN
(Moussavian & Kuss, 1990). Verheij (1993) defined the new family Sporolithaceae. Braga
et al. (1993) and Verheij (1993) affirm that cell and tetrasporangial sizes are not
sufficient enough to identify a species. Cell sizes are not specific characters in Sporolithon
(Verheij, 1993). Some anatomical characters, pointed out by Verheij (1992) as having value
at species level, are not preservable in the fossil material. However, the number of
additional cell filaments between tetrasporangia, the number of cells in the paraphyses,
the basal layer of elongated cells, and the size of the tetrasporangia may be recognized
in the fossil specimens (Bassi, 1995b; Braga & Aguirre, 1998).

Tetrasporangia occur within surface sori which are subcircular in shape
and of indefinite size. Sori raise from a basal layer of elongated cells, 20-26

mm (M= 23, s.d. 3) high and 8-10 mm (M= 9, s.d. 1) in diameter. Sori normally
become buried within the thallus. Tetrasporangia, ellipsoidal in shape, are 57-73 mm (M= 65, s.d. 8) high and 30-34 mm (M= 32, s.d. 2) in diameter. Approximately
4-5-celled paraphysial filaments developed from subterminal initials and are interspersed
between tetrasporangia.

Remarks. By bibliographical revision of the Palaeogene Italian
species of Sporolithon, some anatomical similarities among the following species
can be recognized: Sporolithon (Archaeolithothamnion) aschersoni
(Schwager) Moussavian & Kuss (1990), A. lugeoni Pfender (1926), A.
praeerithraeum Airoldi (1932), A. johnsoni Mastrorilli (1958), A. bericum
Mastrorilli (1973), A. fabianii Mastrorilli (1973), A. poleoense Mastrorilli
(1973), Sporolithon sp. (Bassi, 1995b). Characters considered to be diagnostic at
the species level by phycologists (Verheij, 1992, 1993; Townsend et al., 1995) have been
described for none of the species listed above, as they have not been recognized as
significant by the authors (Schwager, 1883; Airoldi, 1932; Mastrorilli, 1958, 1973). The
value of these diagnostic characters and their comparison regarding S. aschersoni
have been discussed by Bassi (1995b).

Tetrasporangia grouped in sori as parallel lines (generally twin lines)
of indefinite size. Sori do not raise from a basal layer of elongated cells. Sori normally
become buried within the thallus. Tetrasporangia, ellipsoidal in shape, are 112-122

Remarks. S. sp. 1 occurs only in the samples CNB94-97b,
CNB94-103, CNB94-104. S. sp. 1 differs from S. cf. aschersoni in
having larger tetrasporangia arranged in parallel lines which form the sori, and the
absence of a basal layer of elongated cells below the tetrasporangia. According to the
direct comparison between S. sp. 1 and the descriptions and illustrations of the Sporolithon
("Archaeolithothamnium" auct.) species sofar recorded in the
Tertiary Piedmont basin and Veneto, any of these latter show tetrasporangia which do not
raise from a basal layer of elongated cells. It is thus needed a revision of the types to
verify the absence/presence of this and others anatomical features.

Remarks. The occurrence or absence of genicula is considered to
informally divide the Corallinaceae into the geniculate (articulated) and nongeniculate
(non-articulated) groupings. The genicula consist of a single uncorticated and uncalcified
tiers or layers of core cells, which can be characterized by secondary pit-connections,
lateral cell fusions, lateral branches, and cortications (Johansen & Silva, 1978;
Woelkerling, 1988). Spores grow within conceptacles which, however, occur externally or in
non-calcified portions of the thallus. Species of geniculate coralline algae are
distributed worldwide in tropical and subtropical oceans (Dawson, 1966; Riosmena-Rodriguez
& Siqueiros-Beltrones, 1996). The true number of geniculate coralline species is still
controversial (Johansen, 1981; Kim, 1990; Riosmena-Rodriguez & Siqueiros-Beltrones,
1996). Taxonomic problems arise when only traditional methods of morphological comparison
are used because of the phenotypic plasticity of geniculate species. The taxonomy of
geniculate corallines has been based on growth-form, method of branching, internal and
external characters of the genicula and intergenicula, and characters of the reproductive
structures (Bressan, 1974; Johansen & Silva, 1978; Norris & Johansen, 1981;
Woelkerling, 1988; Riosmena-Rodriguez & Siqueiros-Beltrones, 1996).

Geniculate corallines are abundant in many of the Cenozoic carbonate
deposits, at places contributing importantly to the total bulk of the rocks. Difficulty in
their study arises mainly from the fact that the classification at genus level of Recent
representatives is based largely on the genicular cell characters and position and nature
of conceptacles. As the genicula are generally not preserved, it has not been possible so
far to apply the systematics of the present-day geniculates. A distinction between the
fossil specimens of geniculate coralline genera has been proposed by Johnson & Ferris
(1950) and Johnson (1964a) (see also Lignac-Grutterink, 1943), but without the possibility
to distinguish genicular and intergenicular cells nor conceptacles.

Due to the absence both of decalcified genicula and conceptacles in our
studied fossil material, we include all the geniculate fragments in the present
"Geniculate corallines sensu lato" group, with any distinction of species
and genera.

Remarks. Trauth (1918) ascribed specimens recorded from the Eocene
of Radstadt (Pongau, Austria) to the genus Lithothamnium as they shown a cell
arrangement "Lithothamnium-type". Pfender (1936) described a crustose
organism from the Cretaceous and Eocene of Europe, Egypt, and Turkey as Pseudolithothamnium
album. Massieux & Denizot (1964) compared the genus Ethelia Weber van
Bosse, 1913 to Pseudolithothamnium Pfender, 1936 and concluded that Ethelia
was a synonym of Pseudolithothamnium. Denizot (1968), however, redefined the genus Ethelia
as a previously designed genus Polystrata Heydrich, 1905. Buchbinder & Halley
(1985, p. 254) recognized Polystrata alba (Pfender) Denizot and affirmed that
'squamariacean' rhodoliths from middle Eocene of Tonga Island are composed only of this
algal species. Moussavian (1988) does not recognize the synonymy among Pseudolithothamnium,
Ethelia and Polystrata because the type-species of these genera are very
similar but not identical (p. 99). Reports of Polystrata alba (=Pseudolithothamnium
album) were published by other authors (Segonzac, 1961; Beckmann & Beckmann, 1966;
Vannucci, 1970; Moussavian, 1984, 1988). The taxonomy of Polystrata is discussed in
detail by Massieux & Denizot (1964; =Ethelia), Moussavian (1988; =Pseudolithothamnium),
and Bassi (1997).

Morphology. Plants have irregularly layered to foliose
growth-forms; numerous superimposed encrusting layers can develop into sub-ellipsoidal and
sub-discoidal laminated nodules (= rhodoliths). The cavities between each layer may be
filled with micrite.

Vegetative anatomy. Epigenous plant with pseudoparenchymatous
thallus, composed of filaments and organized in a bilateral-radial manner in longitudinal
section. In longitudinal section, each thallus (400-500

mm thick) consists of a single eccentric row (closer to the ventral part of
the crustose thallus) of primigenous filaments composed of tall cells, 47-57 mm (M= 52, s.d. 5) long and 28-36 mm (M= 32, s.d. 4) in diameter. Postigenous
filaments arise plumosely from the outer surface of the cells of primigenous filaments
both upward and downward; the dorsal ones bend progressively upward to become
perpendicular to the surface of the thallus. The postigenous filaments are characterized
by columnar cells, 35-41 mm (M= 38,
s.d. 3) long and 9-15 mm (M= 12, s.d.
3) in diameter, dividing outwards, which reduce their sizes near the outer part of the
thallus. Within a primigenous filament, all the successive cells are joined by primary
pit-connections. Successive cells of postigenous filaments are joined by primary
pit-connections. No secondary pit-connections in postigenous filaments have been
recognized in the samples studied. Epithallial cells smaller than those below.
Conceptacles not found.

Remarks. According to the original descriptions of the type
species, the vegetative anatomy of Pseudolithothamnium album Pfender 1936, Polystrata
alba (Pfender) Denizot 1968 and Ethelia alba (Pfender) Massieux & Denizot,
1964 have similar vegetative anatomies. All the three type species show a dimerous
constructional system characterized by primigenous filaments from which the postigenous
ones rise outwards. It follows that the three species are synonyms belonging to the oldest
genus Polystrata Heydrich 1905. Thus, Polystrata alba (Pfender) Denizot,
1968 is the only valid name (Bassi, 1997).

Remarks. The largest living green marine algae belong to the order
Bryopsidales, formerly Siphonales, and of the modern algae they are the least known. Six
genera out of a total of twenty-four calcify. Five of the taxa, namely Halimeda
Lamouroux, Penicillus Lamarck, Rhipocephalus Ktzing, Tydemania
Weber van Bosse, and Udotea Lamouroux have been assigned to the family
Halimedaceae; Pedobesia MacRaild & Womersly has been placed in the family
Bryopsidaceae (Hillis-Collinvaux, 1984). Assignment to these families is based principally
on differences in morphology, reproduction and distribution, although the data available
for some genera are still very limited Hillis, 1991).

Mu (1991) considers the fossil specimens of Halimeda to belong to the
family Udoteaceae, by accepting the classification of Bassoulet et al. (1983). This author
discusses the relationships between Udoteaceae (= Halimedaceae in Hillis, 1991) and
Gymnocodiaceae, and affirms that the erected fossil specimens of the Udoteaceae group have
similar growth-forms, vegetative features, palaeoecological and geographical distribution
of those of the Gymnocodiaceae.

It is evident that problems in determining the systematic position and
classification of Gymnocodiaceae and fossil Udoteaceae are the result of the inadequate
information available regarding the fossil material. In studying fossil calcareous algae
we are not dealing with complete plants, but only with their calcareous skeletons which
are generally in the form of moulds. According to the data presented by Hillis (1991) and
other works about Bryopsidales (International Symposium, Alpine Algae 1993), it is
possible to ascribe the fossil specimens of Halimeda to the family Halimedaceae.